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A. Types of Reactions navigator

  1. Adverse Reaction (any of the following)
  2. Food Hypersensitivity / Allergies
    1. Immunologically mediated reaction to food or additive
    2. Mainly glycoproteins (MW 10-60K)
    3. Cow milk caseins
    4. Whey
    5. Chicken egg white
    6. Peanuts (see below)
    7. Tree nuts
    8. Soybeens
    9. Fish
    10. Shrimp and other shellfish
    11. Strawberries
  3. Food Anaphylaxis - classic hypersensitivity reaction
  4. Food Intolerance - non-immunologically mediated reaction to food or additive
  5. Food Toxicity (Poisoning)
    1. Adverse reaction caused by direct effect of food or additive
    2. Usually due to toxins in food, often produced by microorganism
  6. Food Idiosyncrasy
    1. Nonimmunologically mediated reaction to specific foods or additives by certain groups
    2. Reaction to monosodium glutamate (MSG; also called Chinese Restaurant Syndrome)
  7. Anaphylactoid Reaction
    1. Nonimmune release of chemical mediators
    2. Common reactions to strawberries, wine, egg whites, tomatoes, citrus
  8. Pharmacologic Reactions
    1. Drug-like or pharmacologic effect
    2. Common reactions to ethanol, caffeine
  9. Metabolic Food Reaction
    1. Adverse reaction to food or additive due to specific host reaction
    2. Lactose Intolerance, Celiac Sprue

B. Classificationnavigator

  1. Immunologic
    1. Immediate Hypersensitivity - IgE mediated
    2. Mixed IgE / Cell Mediated reactions (subacute and chronic)
    3. Subacute or Chronic Hypersensitivity - Non-IgE mediated immune mechanisms
    4. Non-IgE types mediated primarily by T cells
  2. IgE Dependent
    1. Urticaria / angioedema
    2. Immediate gastrointestinal reaction
    3. Oral allergy syndrome (pollen-related); rhinitis
    4. Asthma
    5. Anaphylaxis
    6. Food associated, exercise induced anaphylaxis
  3. Subacute or Chronic IgE and/or Cell Mediated
    1. Atopic dermatitis (infant / child)
    2. Eosinophilic gastroenteropathies
  4. Cell Mediated (Delayed Onset)
    1. Dietary protein enterocolitis (infants)
    2. Dietary protein proctitis (infants)
    3. Dietary protein enteropathy (usually due to cow's milk; infants and children)
    4. Celiac disease and dermatitis herpetiformis
  5. Extrinsic
    1. Toxic
    2. Anaphylactoid
    3. Pharmacologic

C. Mechanisms navigator

  1. Food reactions more common in infancy than later
  2. Many specific food reactions are due to immunologic mechanisms
    1. Appear to be triggered by gut penetration of intact antigen (as peptide fragments)
    2. Local allergic reactions in the gut make the mucosa more permeable to larger peptides
    3. Th2 T helper cell dominance appears to play major role
    4. Th2 cells produce interleukin (IL) 4, IL5, IL9, IL13 and other Th2 cytokines
  3. ~35% of adults develop antibodies after milk ingestion (± symptoms)
  4. Properties of Food Antigens
    1. Usually proteins or glycoproteins
    2. MW 18-36K (similar in size to inhalent antigens)
    3. Adequate cooking destroys most antigens, renders food non-allergenic
  5. Cross-Reactions
    1. Plants within same botanical family have potential for cross reactions
    2. Especially true of legumes, real nuts, citrus fruits
    3. Marine animals of same family cross react - crustaceans, mollusks, bony fish
    4. Mammals rarely if ever cross react
    5. Birch pollen cross-reacts with apple; ragweed pollen cross-reacts with melon
    6. Latex IgE can cross-react with banana, alvacado, kiwi, chestnut, soybean, peanut

D. Peanut Allergy [2,3,5]navigator

  1. Increasing prevlance over past several decades for unclear reasons
    1. >1% of children <5 years
    2. Food allergies in >7% of children <4 years overall
    3. >20% of infants with peanut allergies will outgrow their allergy
  2. Genetic Predispoition
    1. Concordance rate 64% in identical and 7% in fraternal twins
    2. Therefore, strong genetic predisposition
  3. Immunology
    1. Sensitization to peanut protein may occur in children due to peanut oil on skin
    2. Peanut protein, not carbohydrate or fat, is immunologic (allergic) target
    3. Eight peanut allergens have been identified (Ara h1-8)
    4. Ara h1 and h2 are the major allergens (vicilin and conglutin families of seed storage proteins)
    5. IgE antibodies specific for peanut protein bind mediate allergy
    6. IgE-peanut protein complex then binds primarily mast cells and basophils
    7. This immune complex binding leads to release of inflammatory mediators
    8. Histamine, prostaglandins, leukotrienes, platelet activating factor (PAF) involved
    9. Cross sensitization to soy protein may also occur
  4. Diagnosis
    1. Typical acute inflamamtory IgE-mediated disease
    2. Clinical sypmtoms usually develop in seconds, but can occur after 2 hours of ingestion
    3. Allergy nearly always requires eating peanut; not usually triggered by skin or air contact
    4. Most occur with skin involvement; 50% respiratory, >30% gastrointestinal tract
    5. Two organ systems occur in >30% and 3 in >20% of intial reactions [5]
    6. Symptoms as below for other hypersensitivity reactions
    7. Evidence of peanut-specific circulating IgE required for definitive diagnosis
    8. Levels of peanut-specific IgE >14 kU/L diagnostic in symptomatic persons
    9. If levels are <14 kU/L, then food challenge may be used
  5. Treatment
    1. All peanut-allergic persons should have an emergency management plan
    2. Includes epinephrine (Epi-Pen®) and antihistamines on hand at all times
    3. Epinephrine IM: 0.01ml of 1:1000/kg q10-20 minutes; maximum 0.5mL
    4. Diphenhydramine oral or IM 1mg/kg up to 75mg maximum
    5. Epinephrine IV for severe hypotension if needed
    6. Oral prednisone 1-2mg/kg to maximum 75mg OR
    7. Methylprednisolone IV 2mg/kg to maximum 250mg
    8. Possible use of H2-receptor antagonists (300mg ranitidine for adults)
    9. Discharge on 3 days of prednisone (1mg/kg po to max 75mg) AND anti-H1 histamine
    10. Any peanut reaction should be evaluated and observed for up to 4 hours (late phase reseponse)
    11. Anti-IgE monoclonal antibody can reduce sensitivity to peanuts [4]

E. Symptoms and Signsnavigator

  1. Most due to activation of mast cells and occur within 4 hours of food ingestion
  2. Symptoms may progress with eventual full blown anaphylaxis
  3. Early: itchy, swollen lips, itchy mouth, swollen tongue, itchy throat, rhinorrhea, itchy eyes
  4. Progression: difficulty swallowing, abdominal cramps, diarrhea, hives, angioedema
  5. Severe: stridor, bronchospasm, nausea, vomiting, hypotension, death
  6. Rarely, if ever, causes isolated rhinitis or asthma (except some peanut allergies)
  7. Most children grow out of their food allergies

F. Evaluationnavigator

  1. Careful history about foods and amounts ingested is crucial
  2. Note that foods eaten >4 hours from reaction probably not implicated
  3. Physical examination directed at signs described above
  4. Total IgE levels and presence of eosinophilia are non-specific
  5. Skin Testing
    1. Subcutaneous skin test are gold standard for detection of food specific IgE
    2. Patient should be off of antihistamines for appropriate length of time
    3. Positive (histamine) and negative (saline-glycerine) control skin tests used
    4. Positive reaction defined as wheal diameter at least 3mm
    5. Intradermal reactions should not be used
  6. Oral challenges are only attempted when foods cannot be avoided easily

G. Food Additivesnavigator

  1. Sulfites
    1. Bacterial inhibitors, anti-fermentors, preservatives, anti-browning for vegetables
    2. Vast majority of reactions are asthmatic in nature
    3. Sulfur dioxide may be released and cause bronchospasm
    4. Reactions can be confirmed with oral challenge in supervised setting only
    5. Treatment by avoidance
  2. Monosodium Glutamate (MSG)
    1. First reported cases involved "Chinese Restaurant Syndrome"
    2. Headache, occipital burning, chest tightness, nausea and sweating
    3. Usually 15-20 minutes after ingestion
    4. Asthmatics are more susceptible, with early or late reactions, may be severe
    5. Reactions can be confirmed with oral challenge in supervised setting only
  3. Food Dyes
    1. Two Types: Azo group (-N=N-) and non-Azo group
    2. Tartrazine and other azo dyes sometimes implicated in urticaria
    3. No association between non-Azo dyes and urticaria

H. Treatmentnavigator

  1. Directed at symptoms
  2. High dose antihistamines useful for urticarial symptoms
  3. Asthma and/or bronchospasm is treated as usual
  4. Large fluid bolus and epinephrine may be required
  5. Vasopressor support may be necessary
  6. Treatment with anti-IgE monoclonal Ab can reduce peanut and other food allergies [4]

References navigator

  1. Sicherer SH. 2002. Lancet. 360(9334):701 abstract
  2. Sampson HA. 2002. NEJM. 346(17):1294 abstract
  3. Lack G, Fox D, Northstone K, Golding J. 2003. NEJM. 348(11):977 abstract
  4. Leung DY, Sampson HA, Yunginger JW, et al. 2003. NEJM. 348(11):986 abstract
  5. Burks AW. 2008. Lancet. 371(9623):1538 abstract